1. Field of the Invention
The present invention relates to a supervising or monitoring system and a supervising or monitoring method for an electrical power distribution system, particularly a public utility electrical power distribution system providing power to a plurality of consumers which typically are domestic, commercial and industrial. The aim of monitoring is to provide information for improved control of the distribution system
2. Description of the Related Art
Methods have been proposed in which past power loads are analyzed by classification of commercial areas, residential areas and the like, for the purpose of controlling a distribution system. Power loads of distribution feeders (distribution lines) or respective sections of the distribution feeders are predicted from the past record of their power consumption. See E. Handschin et al.: "Bus Load Modelling and Forecasting", IEEE Transaction on Power Systems, Vol. 3, No. 2, May 1988 and C. S. Chen et al.: "ENERGY LOSS REDUCTION BY CRITICAL SWITCHES", IEEE 92 SM 502-5 PWRD, 1992).
Similarly, JP-B-60-53528(1985) discloses a method of predicting currents by proportionally distributing a transmitting current of a distribution feeder to respective sections by using previously memorized power demand amount curves for weekdays and for holidays with respect to the sections.
Further, conventional supervisory technologies, using electrical values which are obtained by predicting the load or the current, are limited to local improvements in which operationally inappropriate conditions are treated in a symptomatic way.
The present inventors believe that there are the following problems in these methods.
(1) Since a power load curve is employed which has been obtained previously by measurement or the like, in the case where an electric facility connected to a distribution feeder, especially an electric facility having a large capacity, is in an irregular and unpredicted operational state which is different from the power load curve (for instance, when there occurs a special holiday of a factory, a breakdown of large equipment or the like), the prediction error is significantly increased.
(2) Recently, cases have increased wherein dump power is supplied to a distribution feeder mainly by a factory having a power generating facility or the like. In this case, since the value of the dump power changes at any time according to the situation in the factory, the supervisory method in which the power load curve has previously been established becomes inappropriate.
(3) It has been an assumption that the flow direction of power (power tidal flow direction) is only one-directional flow from a higher level power network to a lower level power network. Therefore, when a large amount of dump power is supplied from factories and the like to distribution feeders in the future, there will be many cases wherein power flows towards a higher level power network, and it is difficult to predict electrical values with high accuracy by the conventional technologies which do not consider the power flow in both directions.
(4) In conventional supervisory control technologies, there has been no recognition of sampling of portions necessitating improvement in a general way, and there has been no technology of sampling an operational state (for instance, excessive voltage drop, increase in transmission loss, increase in harmonics) of a system to be improved with priority, as a whole, and therefore, the improvement of the operational state of a system has often been carried out locally. As a result, the improvements have not necessarily been performed in a manner having a large improvement effect, and from this point of view, the promotion of improvement efficiency is desired.
(5) It is not possible to specify the cause of a deterioration of the operational state, since the operational state of a system is not grasped in a broad view.